1. Field of the Invention
This invention relates to the regulating of the quantity of light from a light source comprising semiconductor lasers arranged in an array form.
2. Description of the Prior Art
Generally, the method of using a semiconductor laser as a so-called array-like light source having a plurality of independently drivable light-emitting points has various merits. Particularly, where it is used as an image recording light source in a laser beam printer or the like, the use of an array-like light source is very effective for the reasons that:
(1) a plurality of scanning lines can be recorded or displayed at a time and this leads to a high speed recording or display;
(2) therefore, the speeds of a galvanomirror, a rotatable polygonal mirror, etc., that deflect the laser beams may be slow; and
(3) the power of the semiconductor laser may be low and this is advantageous in view of deterioration.
However, the use of an array-like light source results in the following problems:
(1) the characteristics of individual lasers are irregular; and
(2) the speed of deterioration differs from one laser to another (due to the difference in frequency of use).
Therefore, a quantity-of-light regulating mechanism is necessary so that individual semiconductor lasers arranged in an array form may provide the same quantity of light. As an example of such a method, there is a method as shown in FIG. 1 of the accompanying drawings. This is a method whereby the back beams 1a, 1b and 1c of a semiconductor laser array 1 are received by a large detector 2 to detect the quantity of light of each beam. In this method, a large detector which covers the expanse of each emitted beam is necessary to detect the integrated value of the quantity of light of each semiconductor laser and the lasers must be turned on one by one to detect the quantity of light in time-series fashion. Accordingly, the number of arrays of semiconductor lasers is increased and the trouble of turning on and off the lasers successively exists. Moreover, the size of the detector is large and high-speed regulation of the quantity of light is difficult.